Germany is a member of the Schengen Area, which means EU citizens do not require a visa. A valid identity card resp. passport, which is valid for at least four months from your date of arrival is sufficient.
Citizens of all other countries will generally need a visa. The European Community has waived the visa requirement for some of these countries. Nationals of these countries do not require a visa for visits to Germany lasting no longer than three months in a six-month period. An adequate travel medical insurance for the stay is necessary.
For citizens who needs to hold a visa to EU-countries please apply for a visa on time at the embassy of your home country. On their websites you can find online forms to fill in and additional information.
Please inform yourself in time about the entry requirements! Without warranty!
For more information please visit the website of the Federal Foreign office in Germany.